Force the use of secure TLS config

This change updates the TLS config used by all pinniped components.
There are no configuration knobs associated with this change.  Thus
this change tightens our static defaults.

There are four TLS config levels:

1. Secure (TLS 1.3 only)
2. Default (TLS 1.2+ best ciphers that are well supported)
3. Default LDAP (TLS 1.2+ with less good ciphers)
4. Legacy (currently unused, TLS 1.2+ with all non-broken ciphers)

Highlights per component:

1. pinniped CLI
   - uses "secure" config against KAS
   - uses "default" for all other connections
2. concierge
   - uses "secure" config as an aggregated API server
   - uses "default" config as a impersonation proxy API server
   - uses "secure" config against KAS
   - uses "default" config for JWT authenticater (mostly, see code)
   - no changes to webhook authenticater (see code)
3. supervisor
   - uses "default" config as a server
   - uses "secure" config against KAS
   - uses "default" config against OIDC IDPs
   - uses "default LDAP" config against LDAP IDPs

Signed-off-by: Monis Khan <mok@vmware.com>

internal/net/phttp/phttp_test.go

@@ -0,0 +1,116 @@
+// Copyright 2021 the Pinniped contributors. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package phttp
+
+import (
+	"context"
+	"crypto/tls"
+	"crypto/x509"
+	"net/http"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"k8s.io/apimachinery/pkg/util/net"
+	"k8s.io/client-go/util/cert"
+
+	"go.pinniped.dev/internal/crypto/ptls"
+	"go.pinniped.dev/internal/testutil/tlsserver"
+)
+
+// TestUnwrap ensures that the http.Client structs returned by this package contain
+// a transport that can be fully unwrapped to get access to the underlying TLS config.
+func TestUnwrap(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name string
+		f    func(*x509.CertPool) *http.Client
+	}{
+		{
+			name: "default",
+			f:    Default,
+		},
+		{
+			name: "secure",
+			f:    Secure,
+		},
+	}
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			p, err := x509.SystemCertPool()
+			require.NoError(t, err)
+
+			c := tt.f(p)
+
+			tlsConfig, err := net.TLSClientConfig(c.Transport)
+			require.NoError(t, err)
+			require.NotNil(t, tlsConfig)
+
+			require.NotEmpty(t, tlsConfig.NextProtos)
+			require.GreaterOrEqual(t, tlsConfig.MinVersion, uint16(tls.VersionTLS12))
+			require.Equal(t, p, tlsConfig.RootCAs)
+		})
+	}
+}
+
+func TestClient(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name       string
+		clientFunc func(*x509.CertPool) *http.Client
+		configFunc ptls.ConfigFunc
+	}{
+		{
+			name:       "default",
+			clientFunc: Default,
+			configFunc: ptls.Default,
+		},
+		{
+			name:       "secure",
+			clientFunc: Secure,
+			configFunc: ptls.Secure,
+		},
+	}
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			var sawRequest bool
+			server := tlsserver.TLSTestServer(t, http.HandlerFunc(func(_ http.ResponseWriter, r *http.Request) {
+				tlsserver.AssertTLS(t, r, tt.configFunc)
+				assertUserAgent(t, r)
+				sawRequest = true
+			}), tlsserver.RecordTLSHello)
+
+			rootCAs, err := cert.NewPoolFromBytes(tlsserver.TLSTestServerCA(server))
+			require.NoError(t, err)
+
+			c := tt.clientFunc(rootCAs)
+
+			req, err := http.NewRequestWithContext(context.Background(), http.MethodGet, server.URL, nil)
+			require.NoError(t, err)
+
+			resp, err := c.Do(req)
+			require.NoError(t, err)
+			require.NoError(t, resp.Body.Close())
+
+			require.True(t, sawRequest)
+		})
+	}
+}
+
+func assertUserAgent(t *testing.T, r *http.Request) {
+	t.Helper()
+
+	ua := r.Header.Get("user-agent")
+
+	// use assert instead of require to not break the http.Handler with a panic
+	assert.Contains(t, ua, ") kubernetes/")
+}